JPH07321533A - Satellite tracking antenna system - Google Patents

Abstract

PURPOSE:To surely acquire a satellite in a short time regardless of fluctuation in electric field strength. CONSTITUTION:The antenna system is provided with an array antenna 11 receiving a radio wave from a satellite, an elevation angle mono-pulse circuit 14 generating each mono-pulse signal from a received signal, an azimuth angle mono-pulse circuit 15, an antenna drive section 17 driving the array antenna in the azimuth angle direction and the elevating angle direction and a control section 16 controlling each section to acquire and trace the satellite. When the direction of an object satellite is not known, the control section 16 controls the antenna drive section 17 and observes a reception level while changing the directivity of the array antenna 11 to search the satellite and detects that the reception level exceeds a prescribed threshold level to acquire and track the satellite. Moreover, when a maximum reception level during satellite search does not exceed an initial level of the threshold level even not once, the threshold level is set again based on a maximum reception level. Thus, even when the electric field strength is fluctuated, the satellite is surely acquired in a short time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a BS antenna device for receiving satellite broadcasting (BS) in a mobile body such as an automobile, and in particular, a satellite tracking antenna capable of accurately and quickly capturing a satellite to ensure good reception. Regarding the device.

[0002]

2. Description of the Related Art With recent advances in communication technology, radio communication using radio waves has been adopted in various fields. That is, in addition to conventional TV broadcasting, radio broadcasting, and wireless communication, various mobile communication, satellite communication, and the like have become popular.

In such wireless communication, especially satellite communication, weak radio waves from the satellite must be received. Therefore, the most important thing is how to efficiently receive and effectively use radio waves. For this purpose, attempts have been made to receive more radio waves by using a plurality of antennas.

An array antenna is a typical example of such an attempt. With this array antenna, high gain,
That is, the antenna gain having a very narrow beam is arranged in a line or in a plane, and the high frequency signal outputs of the plurality of antenna elements are combined to increase the antenna gain.
The gain can be improved by increasing the number of antenna elements, and this array antenna is very effective for receiving weak radio waves.

By the way, in a moving body such as an automobile,
In order to receive satellite broadcasting, an antenna element having a high gain, that is, a very narrow beam, such as an array antenna, is used, and the azimuth (azimuth) and elevation (elevation) of the beam are changed according to the movement of the moving body. ) Control
A satellite tracking function is required to keep the beam in the satellite direction.

A phase monopulse system is a typical example of such a satellite tracking method. The phase monopulse system is a system in which an angle error between the antenna direction and the radio wave arrival direction, that is, the satellite direction is obtained by detecting the phase difference between a pair of antenna outputs.

[Related Art] As such a monopulse antenna, for example, there is Japanese Patent Application No. 5-124297. Hereinafter, this will be described with reference to FIG.

As shown in FIG. 1, this antenna device is
4 arranged in a matrix of two rows above and below and two rows left and right
Array antenna 1 including two sub-array antennas 1 to 4
1 is provided. The array antenna 11 is a turntable 6
It is fixed to an elevation drive mechanism (not shown) mounted on the top. The antenna driving unit 17 drives the turntable 6 to rotate in the azimuth direction and drives the elevation driving mechanism in the elevation direction.

Further, this antenna device has an upper combiner 12-1 for combining the outputs of the two upper sub-arrays 3 and 4.
, A lower combiner 12-2 that combines the outputs of the two lower sub-arrays 1 and 2, and a left combiner 13-1 that combines the outputs of the two sub-arrays 3 and 1 on the left side when viewed from the rear of the antenna.
, A right combiner 13-2 for combining the outputs of the two right sub-arrays 4 and 2, and an elevation angle monopulse circuit 14 for detecting the phase difference between the upper and lower combiner outputs and outputting an elevation angle monopulse signal. And an azimuth monopulse circuit 15 that outputs a azimuth monopulse signal by detecting the phase difference between the left synthesizer output and the right synthesizer output, and control of the antenna drive unit 17 based on the elevation monopulse signal and the azimuth monopulse signal. It has the control part 16 which performs.

The elevation monopulse signal has an in-phase component (Eco
sθ) and a quadrature component (Esinθ), the azimuth angle monopulse signal has an in-phase component (Acosφ) and a quadrature component (Acosφ).
sin φ).

That is, in this monopulse antenna,
Divide the array antenna into four sub-array antennas,
The output from the top two sub-arrays and the bottom two
The output from the two sub-arrays is combined with the output from the two sub-arrays, and the output from the two sub-arrays on the left is combined with the output from the two sub-arrays. The phase difference between the two is detected from the synthesized one, and a monopulse signal in the azimuth direction is generated.

By controlling the driving of the antenna in the azimuth direction and the elevation angle direction based on the monopulse signal thus obtained, the beam direction of the antenna can be directed to the arrival direction of the radio wave.

As the reception output, the output of the upper combiner 12-1 and the output of the lower combiner 12-2 are combined, or the output of the left combiner 13-1 and the output of the right combiner 13-2 are combined. Obtained by synthesizing.

Next, the principle of the phase monopulse system will be described with reference to FIG. This figure shows the combined output of the left sub-arrays 1 and 3 and the right sub-arrays 2 and 4 in FIG.
2 shows a case where an azimuth angle monopulse signal is obtained from the combined output of 1 to obtain an azimuth angle error (that is, an angle error in the horizontal plane of the antenna direction with respect to the satellite direction).

As shown in FIG. 2, if there is an azimuth angle error Φ between the front direction of the antenna and the satellite direction, 2 from the satellite.
A path length difference occurs up to one antenna, and a phase difference (hereinafter referred to as an azimuth angle phase difference) φ corresponding to the path length difference occurs between the two antenna outputs. The relationship between the azimuth angle error Φ and the azimuth angle phase difference φ is expressed by the following equation (1).

[0016] _{φ = 2π (L A sinΦ)} / λ ...... (1) Here, lambda is the wavelength of the received radio wave, the L _A is the phase distance between the centers of the left and right sub-array antenna.

Therefore, the azimuth angle error Φ can be obtained by detecting the azimuth angle phase difference φ. This azimuth angle phase difference φ is detected by the azimuth angle monopulse circuit 15.

In the azimuth monopulse circuit 15, the composite output of the left sub-array and the composite output of the right sub-array are input in phase to the phase comparator to obtain the in-phase component A cos φ, and one of the antenna outputs is 90 degrees out of phase. After that, the quadrature component Asi is input to the phase comparator.
Get nφ. That is, the combined output of the right sub-arrays 2 and 4 is divided into two in-phase by the in-phase distributor 21 and input to the phase comparators 23 and 24, and the combined output of the left sub-arrays 1 and 3 is supplied to the in-phase and This and 90 ° phase-shifted signals are distributed and input to the phase comparators 23 and 24, respectively. And the phase comparator 2
An azimuth monopulse signal is output from 3 and 24. That is, the phase comparator 23 outputs the in-phase component Acosφ, and the phase comparator 24 outputs the quadrature component Asinφ.

From these two components, the azimuth angle amplitude A and the azimuth angle phase difference φ of the received signal are calculated as the sum of squares ((2) which will be described later).
Equation) and the inverse tangent calculation (Equation (3) described later). In the configuration example of FIG. 1, these calculations are performed by the microprocessor or the like included in the control unit 16.

By the way, in such a satellite tracking antenna, it is necessary to search and capture the satellite direction when the satellite direction becomes unknown, such as immediately after the power is turned on or after the building is shielded. is there. Hereinafter, the conventional search operation for capturing the satellite will be described with reference to FIG.

FIG. 5 shows the in-phase component and quadrature component of the azimuth angle monopulse signal with respect to the azimuth angle error Φ, and the relationship between the azimuth angle amplitude A and the azimuth angle phase φ obtained from each component.

As shown in FIG. 5 (a), the azimuth monopulse signal has a maximum in-phase component (A
cosφ) and an orthogonal component (Asinφ) orthogonal to this (phase difference = 90 °). The azimuth amplitude A is
From these components, it is calculated by the following equation (2), and
As shown in (b).

A = [(Acosφ) ² + (Asinφ) ² ] ^1/2 (2) Further, the azimuth angle phase difference φ is obtained from the following equation (3), and is as shown in FIG. 5 (c). become.

Φ = tan ⁻¹ [(Asin φ) / (A cos φ)] (3) The tracking of the satellite in the azimuth direction is performed by the antenna driver 17 (FIG. 1) so that the azimuth phase φ becomes 0. Although the directional direction of the antenna is changed, as shown in FIG. 5 (c), there are a plurality of directions in which the azimuth phase φ becomes 0, not just the satellite direction (Φ = 0). There is a possibility that the antenna may face a direction other than the satellite direction only by controlling the pointing direction of the antenna so that the antenna becomes 0.

Therefore, a threshold level for determining whether to perform tracking or search is set,
If the azimuth amplitude A is equal to or higher than the threshold level TH, tracking is performed. If the azimuth amplitude A is equal to or lower than the threshold level TH, tracking is not performed, and the antenna is turned and a search for acquisition is performed until the azimuth amplitude A exceeds the threshold level TH. That is, using the threshold level TH, the tracking range is limited to a range where | φ | <180 ° with respect to the phase φ, and tracking control is performed so that the antenna always points in the satellite direction.

[0026]

However, this conventional satellite tracking antenna device has the following problems.

The directivity of the broadcasting antenna mounted on the broadcasting satellite has an elliptical shape centered on the central part of Honshu (near Nagoya and Osaka) and long in the direction of the Japanese archipelago (Tohoku to southwest). Therefore, the strength of the radio waves of satellite broadcasting (electric field strength)
Is not the same all over Japan, but there are regional differences, and Hokkaido, or the Boso Peninsula, which is far from the center of Honshu, is a region where the radio waves are considerably weaker than the central region of Honshu (weak electric field region). In addition, radio waves are attenuated by rain and snow (rainfall attenuation), so when combined with regional differences, the electric field strength of broadcasting satellites fluctuates within a considerable range.

Therefore, when the mobile body (vehicle) equipped with the satellite tracking antenna device moves to a weak electric field area or the radio wave weakens due to rain attenuation, the received power of the antenna decreases, and therefore the waveform of the azimuth monopulse signal. Is Figure 6
The azimuth angle amplitude A decreases as shown in FIG. Therefore, the range in which the amplitude exceeds the threshold level TH is narrowed and the tracking range is reduced. Therefore, when an azimuth angle error occurs due to a response delay of the antenna driving unit 17 (FIG. 1) when the mobile body turns, the tracking error is likely to occur and the tracking performance is deteriorated. Further, when the radio wave becomes weaker, there is no range where the amplitude exceeds the threshold level, and it becomes impossible to capture.

The present invention has been made in order to solve the above-mentioned problems, and the satellite can be reliably and quickly operated even when the electric field strength varies, such as in the case of reception in a weak electric field region or rain attenuation. An object of the present invention is to obtain a satellite tracking antenna device that can capture and keep the tracking range substantially constant according to the fluctuation of the electric field strength.

[0030]

According to a first aspect of the present invention, there is provided a satellite tracking antenna device comprising: (i) an antenna element for receiving radio waves from a satellite; and (ii) level detection for detecting a reception level of the antenna element. Means, (iii) antenna driving means for changing the pointing direction of the antenna element, and (iv) when the satellite direction is unknown, the level detecting means while controlling the antenna driving means to change the pointing direction of the antenna element By searching the satellite by observing the reception level detected by, capture tracking control means for capturing and tracking the satellite by detecting that the reception level exceeds a predetermined threshold level,
(v) A means for holding the maximum value of the reception level during the satellite search by the acquisition tracking control means, and (vi) the reception level never exceeded the threshold level when the search for the predetermined search range was completed. At this time, a setting means for resetting the threshold level based on the maximum value is provided.

According to a second aspect of the present invention, there is provided the satellite tracking antenna device as set forth in the first aspect, wherein when the setting means has finished searching a predetermined search range, the reception level never exceeds the threshold level. , The maximum value of this reception level is compared with a predetermined lower limit value, and as a result of this comparison,
It is characterized in that the threshold level is reset based on the maximum value only when the maximum value of the reception level is equal to or higher than the lower limit value.

A satellite tracking antenna device according to a third aspect of the present invention is (i) an antenna element for receiving radio waves from a satellite, (ii) level detecting means for detecting a reception level of the antenna element, and (iii) Antenna driving means for changing the pointing direction of the antenna element, and (iv) when the satellite direction is unknown, the reception level detected by the level detecting means while controlling the antenna driving means to change the pointing direction of the antenna element. Observing the satellite to search for the satellite and detecting that the reception level exceeds a predetermined threshold level to capture and track the satellite, and (v) the satellite tracking by the acquisition and tracking control means. A means for holding the maximum value of the reception level, and (vi) when the search for the predetermined search range is completed, the range in which the reception level exceeds the threshold level is the predetermined angle range. When was lower, and is characterized in that it comprises setting means for resetting the threshold level, the based on the maximum value.

A satellite tracking antenna device according to a fourth aspect of the present invention is the satellite tracking antenna device according to any one of the first to third aspects, further comprising:
After the resetting by the setting means, second setting means for resetting the threshold level based on the reception level at the time when the antenna element is correctly oriented in the satellite direction is provided. .

A satellite tracking antenna device according to a fifth aspect of the present invention is the satellite tracking antenna device according to any one of the first to fourth aspects, wherein the satellite search direction by the acquisition and tracking control means is at least one of an azimuth direction and an elevation angle direction. It is characterized by.

[0035]

According to the first aspect of the present invention, when the reception level does not exceed the predetermined threshold level even after the search for the predetermined satellite search range is completed, the threshold level is re-set based on the maximum value of the reception level. setting change)
Is done. Therefore, even if the electric field strength fluctuates, the satellite is reliably captured in a short time.

According to the second aspect of the present invention, when the reception level never exceeds the threshold level at the time when the search for the predetermined search range is completed, and the maximum value of the reception level is not less than the predetermined lower limit value. Only, the threshold level is reset. Therefore, when the maximum value of the reception level is less than the predetermined lower limit value, it is recognized that the antenna device is temporarily in the shadow of the shield, and the threshold level is not changed.

According to the third aspect of the present invention, when the range where the reception level exceeds the threshold level is equal to or less than the predetermined angle range at the time when the search for the predetermined search range is completed, the maximum value is used. Then, the threshold level is reset. Therefore, even when the electric field strength changes, the tracking range is kept substantially constant according to the change in the electric field strength.

In the invention according to claim 4, after the resetting of the threshold level, the resetting of the threshold level is further performed based on the reception level at the time when the antenna element is correctly oriented in the satellite direction. Therefore, even when the electric field strength fluctuates, more stable satellite acquisition / tracking becomes possible.

[0039]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows a satellite tracking antenna device according to an embodiment of the present invention, which has the same configuration as that described as a conventional example as a block diagram. That is, this antenna device includes an array antenna 11 including four sub-array antennas 1 to 4 arranged in a matrix of two rows above and below and two rows left and right. Array antenna 11
Is fixed to an elevation drive mechanism (not shown) mounted on the turntable 6. The antenna driving section 17 drives the turntable 6 to rotate in the azimuth direction and drives the elevation driving mechanism in the elevation direction.

Further, this antenna device has an upper combiner 12-1 for combining the outputs of the two upper sub-arrays 3 and 4.
, A lower combiner 12-2 that combines the outputs of the two lower sub-arrays 1 and 2, and a left combiner 13-1 that combines the outputs of the two sub-arrays 3 and 1 on the left side when viewed from the rear of the antenna.
, A right combiner 13-2 for combining the outputs of the two right sub-arrays 4 and 2, and an elevation angle monopulse circuit 14 for detecting the phase difference between the upper and lower combiner outputs and outputting an elevation angle monopulse signal. And an azimuth monopulse circuit 15 that outputs a azimuth monopulse signal by detecting the phase difference between the left synthesizer output and the right synthesizer output, and control of the antenna drive unit 17 based on the elevation monopulse signal and the azimuth monopulse signal. It has the control part 16 which performs. The control unit 16 has a memory 18 for storing a maximum amplitude value described later.

The elevation monopulse signal has an in-phase component (Eco
sθ) and a quadrature component (Esinθ), the azimuth angle monopulse signal has an in-phase component (Acosφ) and a quadrature component (Acosφ).
sin φ).

By driving and controlling the antenna in the azimuth angle direction and the elevation angle direction based on each monopulse signal obtained in this way, the beam direction of the antenna can be directed to the arrival direction of the radio wave.

As the reception output, the output of the upper combiner 12-1 and the output of the lower combiner 12-2 are combined, or the output of the left combiner 13-1 and the output of the right combiner 13-2 are combined. Obtained by synthesizing.

Also in this device, similarly to the conventional example (FIG. 2), the azimuth angle monopulse signal is obtained from the combined output of the left sub-arrays 1 and 3 and the right side sub-arrays 2 and 4 in FIG. The satellite tracking in the azimuth direction is performed by obtaining the angular error. The details are the same as in the conventional example, and therefore the description thereof is omitted here.

On the other hand, in satellite tracking in the elevation angle direction, an elevation angle monopulse signal is obtained from the composite output of the lower sub-arrays 1 and 2 and the composite output of the upper sub-arrays 3 and 4 in FIG. This is done by calculating the angle error in the vertical plane of the antenna direction. This can be done by configuring the elevation monopulse circuit 14 of FIG. 1 in substantially the same manner as the azimuth monopulse circuit 15 of FIG.

In this case, the elevation angle error between the front direction of the antenna and the satellite direction is Θ, and the phase difference corresponding to the path length difference from the satellite to the upper and lower two sets of antennas (hereinafter referred to as the elevation phase difference) is θ. Then, the relationship between the elevation angle error Θ and the elevation angle phase difference θ is expressed by the following equation (4).

[0048] _{θ = 2π (L E sinΘ)} / λ ...... (4) Here, lambda is the wavelength of the received radio wave, is L _E is the phase distance between the centers of the upper and lower sub-array antenna. Therefore, the elevation angle error Θ can be obtained by detecting the elevation angle phase difference θ.

In satellite tracking in the elevation direction, the elevation phase difference θ is 0.
The antenna driving unit 17 (FIG. 1) changes the pointing direction of the antenna so that This elevation phase difference θ is
The elevation monopulse circuit 14 detects.

In the elevation angle monopulse circuit 14, the composite output of the lower sub-array and the composite output of the upper sub-array are input to the phase comparator in phase to obtain the in-phase component Ecos θ, and the phase of one antenna output is shifted by 90 degrees. Then, the quadrature component Esi
Get nθ.

From these two components, the elevation angle phase difference θ and the elevation angle amplitude E are obtained by the following equations (5) and (6), respectively.

Θ = tan ⁻¹ [(Esin θ) / (Ecos θ)] (5) E = [(Ecos θ) ² + (Esin θ) ² ] ^1/2 (6) Next, as described above The satellite acquisition control of the satellite tracking antenna device having the configuration will be described with reference to FIG. Here, for simplification, a case is shown in which a satellite is searched and tracked only in the azimuth direction using an azimuth monopulse signal.

In the initial state immediately after the power is turned on, the control unit 16
First, the threshold level is set to a predetermined initial value TH (step S101). As this initial value, the minimum value that can be correctly tracked in the strong electric field area (Nagoya, Osaka, etc.) is set.

Next, using this initial value TH, a satellite search is performed for a maximum of one round (360 °) (step S10).
2). During the search, the control unit 16 stores and holds the maximum value of the azimuth angle amplitude A in the memory 18.

When the azimuth amplitude A does not exceed the threshold level TH and cannot be captured within one round (step S103; N), the maximum value of the held azimuth amplitude A is compared with a predetermined lower limit value. (Step S104).

The lower limit value is the amplitude value of the monopulse at the minimum electric field intensity that can be tracked / received (image display) in this antenna device. The radio waves of satellite broadcasting become extremely weak when shielded by a building or the like, and reception becomes impossible when shielded even in a strong electric field area. Therefore, when the maximum value is below the lower limit value (step S104; Y), it is determined that the state is the shield state (step S105), and the search is continued without changing the threshold level (step S106).

On the other hand, when the maximum value is equal to or higher than the lower limit value (step S104; N), it is judged that the receiving point is in the weak electric field area and the currently set threshold level TH is too high for the electric field strength (step S104). (S107), the threshold level is corrected based on the maximum value of the azimuth angle amplitude held during the search (step S108). The correction is performed, for example, by setting the threshold level to 2/3 of the maximum value.
It is done by setting the value of. Then, the search is continued by using the corrected threshold level (step S1).
02).

By correcting the threshold level in this way, unless the moving body (satellite tracking antenna device) enters the shielded state, the satellite is always captured in the search turn of the second lap, and the satellite is captured. It can be performed reliably in a short time.

Further, as described above, when the maximum value during the search on the first lap falls below the lower limit value, the search is continued without changing the threshold level, so that the moving body is temporarily shielded. The situation where the threshold level is changed each time you enter the shadow of an object is avoided.

When the satellite is captured in the first orbit of the search turn (step S103; Y), the threshold level is not corrected and remains the initial value, which is not always a value suitable for the actual electric field strength. Absent. Further, even when the threshold level is corrected based on the maximum value at the time of searching as described above, the rotation speed of the antenna element at the time of searching is relatively high, and the control unit 16 samples the phase monopulse signal. Since the interval is finite, the stored maximum value is not always the value when the azimuth angle error Φ = 0. Therefore, the threshold level value corrected based on this maximum value is not always the optimum value for the actual electric field strength.

Therefore, in the present embodiment, after the satellite is captured and the tracking state is entered, the amplitude value at the time when the antenna accurately points in the satellite direction (Φ = 0, that is, the phase φ = 0) is obtained. Based on this, the threshold level is corrected again and set to the optimum value TH 'for the current electric field strength (step S109). For example, the value is set to 2/3 of the amplitude value at the time of φ = 0.

Thus, by resetting the threshold level to TH 'based on the amplitude value at the time when the antenna faces the satellite, even if the electric field strength fluctuates due to changes in the receiving point, weather, etc. Can be kept almost constant, and good tracking characteristics can always be maintained.

That is, as shown in FIG. 4, the tracking range is expanded from R to R'by correcting the threshold level from the initial value TH to TH '. Therefore, for example, even if the azimuth error occurs due to the response delay of the antenna driving unit 17 (FIG. 1) when the mobile body turns, stable tracking is possible without causing tracking deviation.

When the threshold level correction is completed in this way, the satellite tracking mode is then entered to perform tracking (step S110). Even in the tracking mode, when tracking becomes impossible due to shielding or the like and the satellite goes out of the tracking range (step S1
11; Y), and returns to the capture mode (step S10).
2) Recapture the satellite again.

As described above, in the present embodiment, even if the radio wave is weak enough that the maximum value of the azimuth angle amplitude does not exceed the initial value of the threshold level, the threshold level itself is changed to a low value and the amplitude is changed. In order to secure the range in which the value exceeds the threshold level, it is possible to avoid the situation where satellites cannot be captured as in the conventional case. Further, by resetting the threshold level based on the amplitude value at the time when the antenna element is oriented in the satellite direction, good tracking characteristics are maintained even when the electric field strength changes.

In the present embodiment, when the satellite direction becomes unknown, the reception level is the initial value of the threshold level in a predetermined range (for example, all azimuth angle directions), that is, the value at which tracking is normally performed in the strong electric field area. (Azimuth phase φ
However, if the satellite does not exceed the threshold level even once, the maximum value of the reception level during the previous search orbit ((value of −180 ° <φ <180 °)) That is, the threshold level value is corrected based on the value when the antenna is oriented almost in the satellite direction). Therefore, since the threshold level is set to a value (higher value) that matches the strong electric field area first, it is possible to capture an appropriate satellite without capturing a weak reflected wave or capturing a satellite by the side lobe. It will be possible.

Further, when the threshold level value is corrected according to the variation of the electric field strength due to the region or the weather,
The threshold level is not set to an unreasonably low value because the threshold level is set only based on the reception level when the antenna is oriented almost in the satellite direction. Therefore, it is possible to always quickly and surely acquire the satellite. Moreover, even if the electric field strength temporarily drops due to rainfall / scintillation and falls below the threshold level, the search turn is swiftly performed and the threshold level value is reset to a value corresponding to the lowered electric field strength. Tracking can be continued without waiting for the reception level to recover,
It is possible to always maintain a good reception state.

In the above embodiment, the threshold level is corrected when the maximum value of the azimuth angle amplitude does not exceed the initial value of the threshold level in the search for the first round. It is more effective to perform the threshold level correction in the same manner even when the angle range in which the azimuth angle amplitude value exceeds the initial value of the threshold level is below a certain value in the eye search. In this case, the angular range in which the value of the azimuth angle amplitude exceeds the initial value of the threshold level in the search for the first round is stored in the memory 18, and this may be compared with the above-mentioned constant value.

Although the satellite capturing operation in the azimuth direction has been described in this embodiment, the same applies to the elevation direction. By combining the two, it is possible to acquire satellites quickly and accurately, and it is possible to realize stable tracking by expanding the satellite tracking range.

[0070]

As described above, according to the first aspect of the present invention, when the reception level has never exceeded the predetermined threshold level at the time when the search for the predetermined satellite search range is completed, the reception level is not exceeded. Since the threshold level has been reset based on the maximum value of, even if the electric field strength fluctuates (decreases) due to the influence of the receiving point or the weather, it is possible to reliably and quickly capture the satellite. it can.

According to the second aspect of the present invention, the reception level never exceeds the threshold level when the search for the predetermined search range is completed, and the maximum value of the reception level is not less than the predetermined lower limit. Only when the threshold level is reset, the threshold level is reset. Therefore, if the maximum value of the reception level is less than the predetermined lower limit value, the threshold level is not changed. Therefore, for example, it is possible to avoid a situation in which the threshold level is changed every time the antenna device temporarily enters the shadow of the shield.

According to the third aspect of the invention, when the range in which the reception level exceeds the threshold level is equal to or less than the predetermined angle range at the time when the search for the predetermined search range is completed, the maximum value is obtained. Since the threshold level is reset based on the above, even if the electric field strength fluctuates, the tracking range is kept substantially constant according to the fluctuation of the electric field strength. Therefore, the tracking range does not become narrow depending on the receiving point and the weather condition, and it is possible to always obtain stable satellite acquisition / tracking performance.

According to the fourth aspect of the present invention, after the threshold level is reset, the threshold level is reset based on the reception level at the time when the antenna element correctly points in the satellite direction. Therefore, the threshold level is set according to the accurate reception level (electric field strength), and more stable satellite acquisition / tracking is possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a satellite tracking antenna device according to an embodiment of the present invention.

FIG. 2 is a principle diagram for obtaining an azimuth monopulse signal.

3 is a flow chart for explaining a satellite capturing operation of the apparatus of FIG.

FIG. 4 is a diagram showing characteristics of an azimuth monopulse signal, an azimuth amplitude and an azimuth phase with respect to an azimuth, and a range of a satellite tracking range with respect to a change in threshold level.

FIG. 5 is a diagram showing characteristics of an azimuth angle monopulse signal, an azimuth angle amplitude, and an azimuth angle phase with respect to an azimuth angle.

FIG. 6 is a diagram showing characteristics of an azimuth angle monopulse signal, an azimuth angle amplitude, and an azimuth angle phase with respect to an azimuth angle and a width of a satellite tracking range when the electric field strength is changed.

[Explanation of symbols]

 1 to 4 sub-array antenna 6 turntable 11 array antenna 12-1 upper combiner 12-2 lower combiner 13-1 left combiner 13-2 right combiner 14 elevation monopulse circuit 15 azimuth monopulse circuit 16 controller 17 antenna drive Department

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Kunori Nishikawa Aichi Prefecture, Aichi-gun, Nagakute-machi, Nagakage, No. 41 Yokomichi, Toyota Central Research Institute Co., Ltd. (72) Eiji Teramoto, Aichi-gun, Aichi-gun, Nagakute-machi 1 at 41 Central Road, Nagatoji Toyota Central Research Institute Co., Ltd. (72) Inventor Toshiaki Watanabe 1 in 41, Nagakute Town, Aichi-gun, Aichi Prefecture Toyota Central Research Institute at 42 Japan (72) Inventor Masaaki Ogawa 1 in 41, Yokoshiro, Nagakute-cho, Aichi-gun, Aichi Prefecture Toyota Central Research Institute Co., Ltd. (72) Inventor Makoto Morita 1 Toyota-cho, Toyota-shi, Aichi Prefecture Toyota Motor Corporation (72) Inventor Atsushi Ozaka Aichi Prefecture 1 Toyota-cho, Toyota-shi Toyota Motor Co., Ltd. (72) Inventor Kojiro Chikazawa 1-2-2 Gosho-dori, Hyogo-ku, Kobe-shi, Hyogo No. 28 FUJITSU TEN within Co., Ltd. (72) inventor Katsumi Sakata, Hyogo Prefecture, Kobe City, Hyogo-ku, Goshodori 1-chome No. 2 No. 28 FUJITSU TEN within Co., Ltd.

Claims (5)

[Claims] 1. An antenna element for receiving a radio wave from a satellite, a level detecting means for detecting a reception level of the antenna element, an antenna driving means for changing a directing direction of the antenna element, and a satellite direction when the satellite direction is unknown. While controlling the antenna drive means to change the pointing direction of the antenna element, the reception level detected by the level detection means is observed to search for a satellite, and it is detected that the reception level exceeds a predetermined threshold level. Acquisition and tracking control means for capturing and tracking satellites by means of this, means for holding the maximum value of the reception level during the satellite search by this acquisition and tracking control means, and the reception level even once when the search for the predetermined search range is completed. Setting means for resetting the threshold level based on the maximum value when the threshold level is not exceeded. A satellite tracking antenna device characterized in that 2. The apparatus according to claim 1, wherein the setting means, when the reception level has never exceeded the threshold level at the time when the search for the predetermined search range is completed,
The maximum value of the reception level is compared with a predetermined lower limit value, and as a result of this comparison, the threshold level based on the maximum value is reset only when the maximum value of the reception level is equal to or higher than the lower limit value. Satellite tracking antenna device. 3. An antenna element for receiving radio waves from a satellite, a level detecting means for detecting a reception level of the antenna element, an antenna driving means for varying a pointing direction of the antenna element, and a satellite direction when the satellite direction is unknown, While controlling the antenna drive means to change the pointing direction of the antenna element, the reception level detected by the level detection means is observed to search for a satellite, and it is detected that the reception level exceeds a predetermined threshold level. Acquisition and tracking control means for capturing and tracking satellites by means of a means, means for holding the maximum value of the reception level during the satellite search by this acquisition and tracking control means, and at the time when the search of a predetermined search range is completed, the reception level When the range above the threshold level is less than or equal to the predetermined angle range, the threshold level is reset based on the maximum value. Satellite tracking antenna apparatus characterized by comprising setting means for constant for, a. 4. The apparatus according to claim 1, further comprising the step of resetting the threshold level based on the reception level at the time when the antenna element correctly points in the satellite direction after resetting by the setting means. A satellite tracking antenna device comprising: second setting means for resetting. 5. The satellite tracking antenna device according to claim 1, wherein a satellite search direction by the acquisition and tracking control means is at least one of an azimuth direction and an elevation angle direction. .